PLL stereo decoder
The TEA5581 PLL stereo decoder is for car and medium-fi radios. It incorporates all the features provided by the
TEA5580 together with a source selector, muting circuit and output amplifiers with adjustable gain. It also features a
switch for radio or cassette function and a 228 kHz voltage-controlled oscillator (VCO) that is locked to the 19 kHz stereo
pilot tone by a phase-locked loop (PLL) system. Subcarrier frequencies of 19, 38, 57 and 114 kHz are regenerated via
I2L logic from the VCO output.
The PLL phase detector suppresses phase distortion due to the 57 kHz pilot tone from the German ‘Verkehrs Warnfunk’
(VWF) traffic warning system. Typical suppression of the 19 kHz stereo pilot tone is 40 dB. Adjacent channel interference
is prevented by the use of two demodulators, one driven by the 38 kHz decoding signal and the other at 114 kHz to
suppress the third harmonic of the multiplexed input signal.
The gain of the input amplifier can be adjusted by an external resistor and the circuit includes compensation for an IF
filter typical roll-off frequency of 50 kHz (2 dB down at 38 kHz).
The supply voltage range of the circuit is 7 V to 16 V.
• Wide supply voltage range
• Automatic mono/stereo switching (pilot presence detector)
• Smooth stereo-to-mono change-over at weak signals (signal-dependent stereo channel separation)
• LED driver for stereo/mono indicator
third harmonics (114 kHz) of multiplexed signal to prevent interference from strong adjacent channels;
phase distortion due to the 57 kHz signal from VWF transmitters
• Pilot cancelling circuit to give added suppression of 19 kHz stereo pilot tone (up to 25 dB)
• IF filter roll-off compensation
• Source selector for radio or cassette input (typ. 90 dB)
• Mute circuit for 90 dB (typ.) muting of the output level
• Matrix and two output buffers with adjustable gain (max. 20 dB).
TEA5581 : 16-lead DIL; plastic (SOT38); SOT38-1; 1996 August 16.
TEA5581T: 16-lead mini-pack; plastic (SO16L; SOT162A); SOT162-1; 1996 August 16.